PyJWT: Public keys in DER form are accepted as HMAC secrets, bypassing the CVE-2022-29217 guard

{
  "id": "7a79ec944bcb08160d5572d93ff47762959c929d55ebc4dafed5c3ccd8c2c935",
  "url": "https://osv.dev/vulnerability/CVE-2026-102271",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "PyJWT: Public keys in DER form are accepted as HMAC secrets, bypassing the CVE-2022-29217 guard",
    "summary": "PyJWT is a Python implementation of JSON Web Token standards. From 2.4.0 until 2.14.0, PyJWT HMACAlgorithm.prepare_key is affected because asymmetric-key guard relies on textual markers that are absent from DER encoding. This occurs when an application mixes HMAC and asymmetric algorithms and supplies a DER public key as the shared verification key. As a result, PyJWT uses public DER bytes as an HMAC secret. Consequently, an attacker who knows the public key can forge authenticated HMAC tokens. This issue is fixed in version 2.14.0.",
    "evidence": "osv:CVE-2026-102271",
    "products": [],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-102271",
      "aliases": [
        "CVE-2026-102271",
        "GHSA-p4g4-x82p-q773",
        "PYSEC-2026-4149"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/jpadilla/pyjwt",
              "type": "GIT",
              "events": [
                {
                  "introduced": "83ff831a4d11190e3a0bed781da43f8d84352653"
                },
                {
                  "fixed": "c6fe464b356ff4b1ebc9ba62172d331a40aa27df"
                },
                {
                  "fixed": "2798504fa2663364573cf2d1043d8d7fef389499"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "cpe": "cpe:2.3:a:pyjwt_project:pyjwt:*:*:*:*:*:*:*:*",
                    "range": [
                      {
                        "introduced": "2.4.0"
                      },
                      {
                        "fixed": "2.14.0"
                      }
                    ],
                    "source": "CPE_RANGE"
                  },
                  {
                    "range": [
                      {
                        "fixed": "2798504fa2663364573cf2d1043d8d7fef389499"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  },
                  {
                    "range": [
                      {
                        "fixed": "c6fe464b356ff4b1ebc9ba62172d331a40aa27df"
                      }
                    ],
                    "source": "REFERENCES_TAG",
                    "original_tag": "2.14.0"
                  }
                ]
              }
            }
          ],
          "versions": [
            "2.13.0",
            "2.12.1",
            "2.12.0",
            "2.11.0",
            "2.10.1",
            "2.10.0",
            "2.9.0",
            "2.8.0",
            "2.7.0",
            "2.6.0",
            "2.5.0",
            "2.4.0"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-102271.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:52.951621933Z",
      "provider": "osv",
      "references": [
        "https://github.com/jpadilla/pyjwt/releases/tag/2.14.0",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/102xxx/CVE-2026-102271.json",
        "https://github.com/jpadilla/pyjwt/security/advisories/GHSA-p4g4-x82p-q773",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-102271",
        "https://github.com/jpadilla/pyjwt/commit/2798504fa2663364573cf2d1043d8d7fef389499"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-347"
        ],
        "cna_assigner": "GitHub_M",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/102xxx/CVE-2026-102271.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-102271",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 521861,
  "published_at": "2026-09-28T20:31:53.066+00:00"
}